A 5.8-magnitude quake hit Puerto Rico before dawn Monday, unleashing small landslides, causing power outages and severely cracking some homes. It was one of the strongest quakes yet to hit the US territory that has been shaking for the past week.

There were no immediate reports of casualties.

The quake was followed by a string of smaller temblors, including another quake measured at magnitude 5 that struck later Monday, at 10:51 a.m. shaking power lines and frightening residents of southern Puerto Rico who had been waiting outside their homes due to fears the buildings were damaged and unstable.

The first quake struck at 6:32 a.m. just south of the island at a relatively shallow depth of 10 km (6 miles), according to the US Geological Service. There was no tsunami threat, officials said.

Power outages were reported in some parts of Puerto Rico following the quake, Angel Vazquez, emergency management director for the southern coastal city of Ponce, told The Associated Press.

“This is one of the strongest quakes to date since it started shaking on Dec. 28,” he said. “It lasted a long time.”

Helicopters buzzed overhead as terrified residents jumped up from their folding chairs every time the earth shook, yelling at others to stay away from power lines.

Dozens of people in a neighborhood called Hope in the southwest town of Guánica walked around with their phones and yelled out the magnitude of the latest earthquakes as they tried to calm children who were forced to open their presents on Three Kings Day, a religious holiday, on streets and sidewalks.

Many already had bags packed in their cars with a change of clothes, food, water and medicine.

Puerto Rico doesn’t have a public earthquake warning system, except for sirens that are supposed to ring in case of a tsunami. Residents in this neighborhood criticized the government for what they believe is a lack of action.

The flurry of quakes in Puerto Rico’s southern region began the night of Dec. 28, with quakes ranging in magnitude from 4.7 to 5.1. Previous quakes of lesser magnitudes in recent days have cracked homes and led to goods falling off supermarket shelves.

Victor Huerfano, director of Puerto Rico’s Seismic Network, told the AP that shallow quakes were occurring along three faults in Puerto Rico’s southwest region: Lajas Valley, Montalva Point and the Guayanilla Canyon. He said the quakes overall come as the North American plate and the Caribbean plate squeezes Puerto Rico, and that it was unclear when they would stop or if bigger quakes would occur.

One of the largest and most damaging earthquakes to hit Puerto Rico occurred in October 1918, when a 7.3-magnitude quake struck near the island’s northwest coast, unleashing a tsunami and killing 116 people.